Method for the telomerisation of non-cyclic olefins

ABSTRACT

The invention relates to a process for the telomerization of acyclic olefins having at least two conjugated double bonds (I) or mixtures in which such olefins are present with nucleophiles (II) using a metal-carbene complex as catalyst.

The present invention relates to a process for the telomerization ofacyclic olefins having at least two conjugated double bonds (I) withnucleophiles (II) using a metal-carbene complex as catalyst.

For the purposes of the present invention, telomerization is thereaction of olefins having conjugated double bonds (conjugated dienes)in the presence of a nucleophile (telogen). The main products obtainedare compounds made up of two equivalents of the diene and one equivalentof the nucleophile.

The products of the telomerization reaction are of industrial importanceas versatile precursors for solvents, plasticizers, fine chemicals andintermediates for active compounds. The octadienol, octadienyl ethers oroctadienyl esters obtainable from butadiene are potential intermediatesin processes for preparing corresponding alkenes.

The telomerization of dienes with nucleophiles is an industriallyinteresting method of adding value to inexpensive, industriallyavailable dienes. Owing to their ready availability, the use ofbutadiene, isoprene or cracker fractions obtained from these dienes isof particular interest. However, to the present time, the telomerizationof butadiene is being employed in practice only by Kuraray in the finechemicals sector for the synthesis of 1-octanol. The reasons whichprevent the wider use of telomerization processes include unsatisfactorycatalyst activities, catalyst productivities and selectivity problemswith telomerization catalysts. Thus, the known telomerization processesresult in high catalyst costs and/or by-products which preventindustrial implementation.

Compounds which have been found to be effective catalysts fortelomerization are, inter alia, halogen-free palladium (0) and palladium(II) compounds (A. Behr, in “Aspects of Homogeneous Catalysis”; editorR. Ugo, D. Reidel Publishing Company, Doordrecht/Boston/Lancaster, 1984,Vol. 5, 3). In addition, compounds of other transition metals such ascobalt (R. Baker, A. Onions, R. J. Popplestone, T. N. Smith, J. Chem.Soc., Perkin Trans. II 1975, 1133-1138), rhodium, nickel (R. Baker, D.E. Halliday, T. N. Smith, J. Organomet. Chem. 1972, 35, C61-C63; R.Baker, Chem. Rev. 1973, 73, 487-530; R. Baker, A. H. Cook, T. N Smith,J. Chem. Soc., Perkin Trans. II 1974, 1517-1524.) and platinum have alsobeen used as catalysts.

The telomerization of dienes is described comprehensively in thetechnical literature. In the telomerization of butadiene with methanol,for example, the abovementioned catalysts generally give mixtures of theproducts 1a, 1b, 2, 3 (below) where X═O, R^(a)=Me. Main products are thedesired, industrially important linear telomers 1a and 1b. However,significant proportions of the branched telomer 2 and of1,3,7-octatriene 3 are formed.

Furthermore, 4-vinyl-1-cyclohexene (Diels-Alder product of butadiene) isformed in variable yields together with, generally in only smallamounts, further by-products. This range of products is generally alsofound when using other nucleophiles having active hydrogen atoms, inwhich case the corresponding radicals of the respective nucleophile areintroduced in place of the methoxy group.

The significant formation of the abovementioned by-products is a furtherfactor which makes implementation of an economical and environmentallyfriendly process extraordinarily difficult. Although telomerization ofbutadiene with methanol has been intensively studied and patented by anumber of companies, the abovementioned problems have not been solvedsatisfactorily.

In a continuous process described by Dow Chemical in WO 91/09822 in1989, in which palladium acetylacetonate/triphenylphosphine is used ascatalyst, catalyst productivities (turnover numbers) up to 44,000 wereachieved. However, the chemoselectivities to the target product 1 atsuch catalyst turnover numbers are <85%.

National Distillers and Chem. Corp. (U.S. Pat. No. 4,642,392, U.S. Pat.No. 4,831,183) described a batch process for the preparation ofoctadienyl ethers in 1987. Here, the product mixture was separated offfrom the catalyst (palladium acetate/5 eq. of triphenylphosphine) bydistillation, leaving the catalyst as a solution in tetraglyme. Thecatalyst can be reused up to twelve times, with further phosphine beingadded each time. However, the first batch gave the linear ether in ayield of only 57% (corresponds to a TON of 2000). The n/iso ratio ofproduct 1 to product 2 is in this case only 3.75:1. In a further patentof National Distillers, the product mixture was separated from thereaction solution by extraction with hexane. The telomerization wascarried out in dimethylformamide or sulfolane using the catalyst mixturepalladium(II) acetate/3 eq. of triphenylphosphinemonosulfonate. Thefirst batch gave the linear telomer with a TON of 900. The selectivityto the linear alcohol was a low 40%.

Longer-chain primary alcohols such as ethanol, propanol and butanol (J.Beger, H. Reichel, J. Prakt. Chem. 1973, 315, 1067) form thecorresponding telomers with butadiene. However, the catalyst activity ofthe known catalysts is in this case even lower than in theabovementioned cases. Thus, under identical reaction conditions[Pd(acetylacetonate)₂/PPh₃/butadiene/alcohol=1:2:2000:5000; 60° C./10h], the telomers of methanol are formed in a yield of 88%, those ofpropanol are formed in a yield of 65% and those of nonanol are formed ina yield of only 21%.

In summary, it can be said that the known palladium-phosphine catalystsfor the telomerization reactions of butadiene with alcohols do not allowsatisfactory selectivities of >95% chemoselectivity andregioselectivity, as required for an ecologically advantageous process,to be achieved.

Like alcohols, carboxylic acids are suitable nucleophiles intelomerization reactions. Acetic acid and butadiene give good yields ofthe corresponding octadienyl derivatives 1a, 1b and 2 with R^(a)=Me—CO,X═O (DE 2 137 291). The ratio of products 1/2 can be influenced via theligands of the palladium (D. Rose, H. Lepper, J. Organomet. Chem. 1973,49, 473). A ratio of 4/1 could be achieved using triphenylphosphine asligand, and the ratio could be increased to 17/1 whentris(o-methylphenyl)phosphite was used. Other carboxylic acids such aspivalic acid, benzoic acid or methacrylic acid and also dicarboxylicacids can likewise be reacted with butadiene.

Shell Oil has described a process based on the telomerization ofconjugated dienes with carboxylic acids for the preparation of α-olefinsin U.S. Pat. No. 5,030,792.

Telomerization reactions in which water is used as nucleophile have beenstudied intensively by, inter alia, Kuraray (U.S. Pat. No. 4,334,117,U.S. Pat. No. 4,356,333, U.S. Pat. No. 5,057,631). Here, phosphines,usually water-soluble phosphines, or phosphonium salts (EP 0 296 550)are usually used as ligands. The use of water-soluble diphosphines asligands is described in WO 98/08 794, and DE 195 23 335 discloses thereaction of alkadienes with water in the presence of phosphonite orphosphinite ligands.

The telomerization of butadiene with nucleophiles such as formaldehyde,aldehydes, ketones, carbon dioxide, sulfur dioxide, sulfinic acids,β-keto esters, β-diketones, malonic esters, α-formyl ketones and silaneshas likewise been described.

Most of the work on telomerization has been carried out using butadiene.However, this reaction can also be applied to other dienes havingconjugated double bonds. These can formally be regarded as derivativesof butadiene in which hydrogen atoms have been replaced by other groups.Isoprene is of particular industrial importance. Since, in contrast tobutadiene, isoprene is an unsymmetrical molecule, telomerization resultsin formation of further isomers (J. Beger, Ch. Duschek, H. Reichel, J.Prakt. Chem. 1973, 315, 1077-89). The ratio of these isomers isinfluenced considerably by the type of nucleophile and the choice ofligands.

Owing to the abovementioned importance of the telomerization productsand the problems associated with the present state of the art, there isa great need for new catalyst systems for telomerization reactions whichmake it possible to carry out the reactions on an industrial scale withhigh catalyst productivity and give telomerization products in highyield and purity.

It has surprisingly been found that the telomerization reactions of anacyclic olefin with a nucleophile are catalyzed by metals of groups 8 to10 of the Periodic Table and particular carbene ligands so as to givehigh conversions and selectivities.

The invention accordingly provides a process for the catalytictelomerization of acyclic olefins having at least two conjugated doublebonds, in particular acyclic olefins of the formula (I)

with at least one nucleophile,

-   -   wherein complexes comprising metals of groups 8 to 10 of the        Periodic Table of the Elements and at least one carbene ligand        having one of the formulae        where    -   R^(X1), R^(X2), R^(X3), R^(X4), R^(X5), R^(X6) are identical or        different and are each H or a linear, branched, substituted or        unsubstituted cyclic or alicyclic aliphatic or aromatic group        having from 1 to 24 carbon atoms,    -   R²; R³ are identical or different and are each a) a linear,        branched, substituted or unsubstituted cyclic or alicyclic alkyl        group having from 1 to 24 carbon atoms,        -   or b) a substituted or unsubstituted, monocyclic or            polycyclic aryl group having from 6 to 24 carbon atoms        -   or c) a monocyclic or polycyclic, substituted or            unsubstituted heterocycle having from 4 to 24 carbon atoms            and at least one heteroatom from the group consisting of N,            O, S,    -   R⁴, R⁵, R⁶, R⁷: are identical or different and are each        -   hydrogen, alkyl, aryl, heteroaryl, —CN, —COOH, —COO-alkyl,            —COO-aryl, —OCO-alkyl, —OCO-aryl, —OCOO-alkyl, —OCOO-aryl,            —CHO, —CO-alkyl, —CO-aryl, —O-alkyl, —O-aryl, —NH₂,            —NH(alkyl), —N(alkyl)₂, —NH(aryl), —N(aryl)₂, —F, —Cl, —Br,            —I, —OH, —CF₃, —NO₂, -ferrocenyl, —SO₃H, —PO₃H₂, where the            alkyl groups have 1-24 carbon atoms and the aryl groups have            from 5 to 24 carbon atoms and the radicals R⁴ and R⁵ may            also be part of a bridging aliphatic or aromatic ring,            with the proviso that when the metal of groups 8 to 10 of            the Periodic Table is Pd, R² and/or R³ have the meaning c),            are used as catalyst.

R² and R³ are in particular a monocyclic or polycyclic ring whichcontains at least one heteroatom selected from among the elementsnitrogen, oxygen and sulfur and may bear further substituents selectedfrom among the groups —CN, —COOH, COO-alkyl, —COO-aryl, —OCO-alkyl,—OCO-aryl, —OCOO-alkyl, —OCOO-aryl, —CHO, —CO-alkyl, —CO-aryl, -aryl,-alkyl, —O-alkyl, —O-aryl, —NH₂, —NH(alkyl), —N(alkyl)₂, —NH(aryl),—N(aryl)₂, —F, —Cl, —Br, —I, —OH, —CF₃, —NO₂, -ferrocenyl, —SO₃H,—PO₃H₂. The alkyl groups have from 1 to 24 carbon atoms and the arylgroups have from 5 to 24 carbon atoms. When Pd is used as metal ofgroups 8 to 10 of the Periodic Table, one or both of the ligands R² andR³ have these meanings.

The radicals R², R³, R⁴, R⁵, R⁶ and/or R⁷ can be identical or differentand may bear at least one substituent from the group consisting of —H,—CN, —COOH, —COO-alkyl, —COO-aryl, —OCO-alkyl, —OCO-aryl, —OCOO-alkyl,—OCOO-aryl, —CHO, —CO-alkyl, —CO-aryl, -aryl, -alkyl, -alkenyl, -allyl,—O-alkyl, —O-aryl, —NH₂, —NH(alkyl), —N(alkyl)₂, —NH(aryl), —N(aryl)₂,—F, —Cl, —Br, —I, —OH, —CF₃, —NO₂, -ferrocenyl, —SO₃H, —PO₃H₂, where thealkyl groups have from 1 to 24, preferably from 1 to 20, carbon atoms,the alkenyl groups have from 2 to 24 carbon atoms, the allyl groups havefrom 3 to 24 carbon atoms and the monocyclic or polycyclic aryl groupshave from 5 to 24 carbon atoms.

The radicals R⁴ to R⁶ may also be covalently bound to one another, e.g.via CH₂ or CH groups.

Substituents having acidic hydrogen atoms can also have metal orammonium ions in place of the protons.

The radicals R² and R³ may be, inter alia, monocyclic or polycyclicrings containing at least one heteroatom. These are, for example,radicals which are derived from five- and six-membered heteroalkanes,heteroalkenes and heteroaromatics such as 1,4-dioxane, morpholine,y-pyran, pyridine, pyrimidine, pyrazine, pyrrole, furan, thiophene,pyrazole, imidazole, thiazole and oxazole. Specific examples of suchradicals R2 and R3 are shown in the table below. In the table below. Inthe table,˜in each case indicates the point of linkage to thefive-membered heterocycle.

For the purposes of the present invention, carbene ligands include bothfree carbenes which can function as ligand and also carbenes coordinatedto metals.

Suitable metals can be, for example, Pd, Fe, Ru, Os, Co, Rh, Ir, Ni orPt.

In the telomerization carried out by the process of the invention, it isin principle possible to use all acyclic olefins having at least twoconjugated double bonds. For the purposes of the present invention, theuse of compounds of the formula (I), in particular 1,3-butadiene andisoprene (2-methyl-1,3-butadiene), is preferred. It is possible to useboth the pure dienes and mixtures in which these dienes are present.

As mixtures comprising 1,3-butadiene/isoprene, preference is given tousing mixtures of 1,3-butadiene or isoprene with other C₃-, C₄- and/orC₅-hydrocarbons. Such mixtures are obtained, for example, in crackingprocesses for the production of ethene, in which refinery gases,naphtha, gas oil, LPG (liquefied petroleum gas), NGL (natural gasliquid), etc, are reacted. The C₄ fractions obtained as by-product inthese processes comprise, depending on the cracking process, variableamounts of 1,3-butadiene. Typical 1,3-butadiene concentrations in the C₄fraction obtained from a naphtha steam cracker are from 20 to 70% of1,3-butadiene.

The C₄ components n-butane, i-butane, 1-butene, cis-2-butene,trans-2-butene and i-butene, which are likewise present in thesefractions, interfere only inconsequentially, if at all, in the reactionin the telomerization step.

Dienes having cumulated double bonds (1,2-butadiene, allene, etc) andalkynes, in particular vinylacetylene can, on the other hand, act asmoderators in the telomerization reaction. It is therefore advantageousto remove the alkynes and possibly the 1,2-butadiene beforehand (e.g. asdescribed in DE 195 23 335). This can, if possible, be carried out bymeans of physical processes such as distillation or extraction. Possiblechemical routes are selective hydrogenation of the alkynes to alkenes oralkanes and reduction of the cumulated dienes to monoenes. Methods ofcarrying out such hydrogenations are prior art and are described, forexample, in WO 98/12160, EP-A-0 273 900, DE-A-37 44 086 or U.S. Pat. No.4,704,492.

As nucleophiles in the process of the invention, preference is given tousing compounds of the formula (II)R¹-Z-R^(1′)  (II)where

-   -   Z is O, N(R^(1″)),N(CH₂CH═CH₂), C(H₂), Si(R^(1″))(OH), C═O,        C(H)(NO₂) or S(O₂), viz.        and R¹, R^(1′) or R^(1″) are identical or different and are each        H, a substituted or unsubstituted, linear, branched or cyclic        alkyl or alkenyl group having from 1 to 22 carbon atoms, a        carboxyl group or an aryl group, where the radicals R¹, R^(1′)        may be joined to one another via covalent bonds and R¹ and        R^(1′) may bear identical or different substituents, e.g. one or        more substituents selected from the group consisting of —CN,        —COOH, —COO-alkyl, —CO-alkyl, -aryl, -alkyl, —COO-aryl,        —CO-aryl, —O-alkyl, —O—CO-alkyl, —N-alkyl₂, —CHO, —SO₃H, —NH₂,        —F, —Cl, —OH, —CF₃, —NO₂. The alkyl groups on the substituents        preferably have from 1 to 24 carbon atoms and the aryl groups on        the substituents preferably have from 5 to 24 carbon atoms.

In a preferred embodiment, compounds of the formula (IIa) or (IIb)

where R¹, R^(1′) are identical or different and are each H, asubstituted or unsubstituted, linear, branched or cyclic alkyl oralkenyl group having from 1 to 22 carbon atoms, a carboxyl group or anaryl group and the radicals R¹, R^(1′) may be joined to one another viacovalent bonds, are used as nucleophile (II).

R¹ and R^(1′) may bear identical or different substituents, e.g. one ormore substituents selected from the group consisting of —CN, —COOH,—COO-alkyl, —CO-alkyl, -aryl, -alkyl, —COO-Aryl, —CO-aryl, —O-alkyl,—O—CO-alkyl, —N-alkyl₂, —CHO, —SO₃H, —NH₂, —F, —Cl, —OH, —CF₃, —NO₂. Thealkyl groups have from 1 to 24 carbon atoms and the aryl groups havefrom 5 to 24 carbon atoms.

As nucleophiles, preference is given to using any compounds having theformula (II). Examples of telogens of the formula (II) are

-   -   water,    -   alcohols and phenols such as methanol, ethanol, n-propanol,        isopropanol, allyl alcohol, butanol, octanol, 2-ethylhexanol,        isononanol, benzyl alcohol, cyclohexanol, cyclopentanol,        2-methoxyethanol, phenol or 2,7-octadien-1-ol,    -   dialcohols such as ethylene glycol, 1,2-propanediol,        1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 2,3-butanediol        and 1,3-butanediol,    -   polyols such as glycerol, glucose, sucrose,    -   hydroxy compounds such as α-hydroxyacetic esters,    -   carboxylic acids such as acetic acid, propanoic acid, butanoic        acid, isobutanoic acid, benzoic acid, 1,2-benzenedicarboxylic        acid, 1,3-benzenedicarboxylic acid, 1,4-benzene-dicarboxylic        acid, 1,2,4-benzenetricarboxylic acid,    -   ammonia,    -   primary amines such as methylamine, ethylamine, propylamine,        butylamine, octylamine, 2,7-octadienylamine, dodecylamine,        aniline, ethylenediamine or hexamethylenediamine,    -   secondary amines such as dimethylamine, diethylamine,        N-methylaniline, bis(2,7-octadienyl)amine, dicyclohexylamine,        methylcyclohexylamine, pyrrolidine, piperidine, morpholine,        piperazine or hexamethylenimine.

Telogens which can themselves be obtained by a telomerization reactioncan be used directly or else be formed in situ. Thus, for example,2,7-octadien-1-ol can be formed in situ from water and butadiene in thepresence of the telomerization catalyst, 2,7-octadienylamine can beobtained from ammonia and 1,3-butadiene, etc.

Particularly preferred telogens are water, methanol, ethanol, n-butanol,allyl alcohol, 2-methoxyethanol, phenol, ethylene glycol,1,3-propanediol, glycerol, glucose, sucrose, acetic acid, butanoic acid,1,2-benzenedicarboxylic acid, ammonia, dimethylamine and diethylamine.

The process of the invention is preferably carried out in the presenceof a solvent.

As solvent, use is generally made of the nucleophile employed, if it ispresent as a liquid under the reaction conditions. However, it is alsopossible to use other solvents. The solvents used should be largelyinert. Preference is given to the addition of solvents when usingnucleophiles which are present as solids under the reaction conditionsor in the case of products which would be obtained as solids under thereaction conditions. Suitable solvents include, inter alia, aliphatic,cycloaliphatic and aromatic hydrocarbons such as C₃-C₂₀-alkanes,mixtures of lower alkanes (C₃-C₂₀), cyclohexane, cyclooctane,ethylcyclohexane, alkenes and polyenes, vinylcyclohexene,1,3,7-octatriene, the C₄-hydrocarbons from C₄ fractions from crackers,benzene, toluene and xylene; polar solvents such as tertiary andsecondary alcohols, amides such as acetamide, dimethylacetamide anddimethylformamide, nitriles such as acetonitrile and benzonitrile,ketones such as acetone, methyl isobutyl ketone and diethyl ketone;carboxylic esters such as ethyl acetate, ethers such as dipropyl ether,diethyl ether, dimethyl ether, methyl octyl ether, 3-methoxyoctane,dioxane, tetrahydrofuran, anisole, alkyl and aryl ethers of ethyleneglycol, diethylene glycol and polyethylene glycol and other polarsolvents such as sulfolane, dimethyl sulfoxide, ethylene carbonate,propylene carbonate and water. Ionic liquids, for example imidazolium orpyridinium salts, can also be used as solvents.

The solvents are used either alone or as mixtures of various solvents ornucleophiles.

The temperature at which the telomerization reaction is carried out isin the range from 10 to 180° C., preferably from 30 to 120° C.,particularly preferably from 40 to 100° C. The reaction pressure is from1 to 300 bar, preferably from 1 to 120 bar, particularly preferably from1 to 64 bar and very particularly preferably from 1 to 20 bar.

In the process of the invention, it is essential that the telomerizationreaction is carried out using catalysts based on metal complexes havingcarbene ligands of the formulae (III) to (VI).

Examples of carbene ligands corresponding to the formulae (III) to (VI)and complexes in which such ligands are present have been described inthe technical literature (W. A. Herrmann, C. Köcher, Angew. Chem. 1997,109, 2257; Angew. Chem. Int. Ed. Engl. 1997, 36, 2162; W. A. Herrmann,T. Weskamp, V. P. W. Böhm, Advances in Organometallic Chemistry, 2001,Vol. 48, 1-69; D. Bourissou, O. Guerret, F. P. Gabbai, G. Bertrand,Chem. Rev. 2000, 100, 39-91).

However, only few examples of carbene ligands and complexes bearingheterocyclic substituents are known (J. C. C. Chen, I. J. B. Lin,Organometallics 2000, 19, 5113).

The catalyst metal of groups 8 to 10 of the Periodic Table can beintroduced into the process in various ways:

-   -   a) as metal-carbene complexes,    -   b) in the form of precursors from which the catalysts are formed        in situ.        Option a)

Metal-carbene complexes have been described in the technical literature(cf. W. A. Herrmann, C. Köcher, Angew. Chem. 1997, 109, 2257; Angew.Chem. Int. Ed. Engl. 1997, 36, 2162; W. A. Herrmann, T. Weskamp, V. P.W. Böhm, Advances in Organometallic Chemistry, 2001, Vol. 48, 1-69; D.Bourissou, O. Guerret, F. P. Gabbai, G. Bertrand, Chem. Rev. 2000, 100,39-91; J. C. C. Chen, I. J. B. Lin, Organometallics 2000, 19, 5113) andare obtainable by various routes. For example, the complexes can beformed by addition of carbene ligand onto metal compounds. This can beachieved with expansion of the ligand sphere or by breaking up of bridgestructures. Metal compounds of the formula I can often be obtained fromsimple compounds of metals of groups 8 to 10 of the Periodic Table, e.g.salts or metal complexes (acetates, acetylacetonates, carbonyls, etc) byreaction with the carbene ligands. A further possibility is thereplacement of ligands coordinated to the central metal by the carbeneligands. In this case, less strongly coordinating ligands (e.g. solventmolecules) are displaced by the carbene ligands.

For the purposes of the present invention, preference is given to usingmetal-carbene complexes having the formula[L_(a)M_(b)X_(c)][A]_(n)   (VII)where

-   -   M is a metal of groups 8 to 10 of the Periodic Table of the        Elements, X is a charged or uncharged, monodentate or        polydentate ligands bound to the metal atom and    -   A is a singly charged anion or the chemical equivalent of a        multiply charged anion, L is one or more ligands of the formulae        III to VI, b is an integer from 1 to 3, a is an integer from 1        to 4×b, c=0 or an integer from 1 to 4×b and n=0 or an integer        from 1 to 6.

The group A is preferably a halide, sulfate, phosphate, nitrate,pseudohalide, tetraphenylborate, tetrafluoroborate, hexafluorophosphateor carboxylate ion, among the latter preferably the acetate ion, or elsea metal complex anion, for example tetrachloropalladate,tetrachloro-aluminate, tetrachloroferrate(II), hexafluoroferrate(III),tetracarbonylcobaltate.

The monodentate or polydentate ligands which may be present in thecomplexes of Fe, Ru, Co, Rh, Ir, Ni, Pd and Pt in addition to thecarbene ligands are shown in the formula (VII) as X. X is hydrogen orthe hydrogen ion, a halogen or halogen ion, pseudohalide, carboxylateion, sulfonate ion, amide group, alkoxide group, acetylacetonate group,carbon monoxide, alkyl radical having from 1 to 7 carbon atoms, arylradical having from 6 to 24 carbon atoms, isonitrile, nitrogen ligand,(for example nitrogen monoxide, nitrile, amine, pyridine), monoolefin,diolefin, alkyne, allyl group, cyclopentadienyl group, π-aromatic orphosphorus ligand which coordinates via the phosphorous atom. Phosphorusligands are preferably compounds of trivalent phosphorus, e.g.phosphines, phosphites, phosphonites, phosphinites. If a plurality ofligands X are present in the metal complex, they can be identical ordifferent.

If the substituents of the carbene ligands of the formulae (III) to (VI)bear functional groups, these can likewise coordinate to the metal atom(chelating coordination, also described as hemilabile coordination inthe literature (J. C. C. Chen, I. J. B. Lin, Organometallics 2000, 19,5113).

Option b)

The metal carbene complexes are formed in situ from precursors andcarbene ligand or a carbene ligand precursor.

As precursors of the metal complexes of groups 8 to 10 of the PeriodicTable, it is possible to use, for example, salts or simple complexes ofthe metals, for example metal halides, metal acetates, metalacetylacetonates, metal carbonyls.

For the purposes of illustration, some specific examples of palladiumcompounds are palladium(II)acetate, palladium(II)chloride, palladium(II)bromide, lithium tetrachloro-palladate, palladium(II)acetylacetonate,palladium(0)-dibenzylideneacetone complexes, palladium(II)propionate,bis(acetonitrile)palladium(II)chloride,bis(triphenylphosphine)-palladium(II)dichloride,bis(benzonitrile)palladium(II)chloride,bis(tri-o-tolylphosphine)-palladium(0). Analogous compounds of the othermetals of groups 8 to 10 of the Periodic Table can likewise be used.

The carbenes of the formulae (III) to (VI) are used in the form of freecarbenes or as metal complexes or are generated in situ from carbeneprecursors.

Suitable carbene precursors are, for example, salts of the carbeneshaving the formulae (VIII) to (XI),

where R², R³, R⁴, R⁵, R⁶, R⁷ are as defined above and Y is a singlycharged anionic group or, corresponding to the stoichiometry, part of amultiply charged anionic group.

Examples of Y are halides, hydrogensulfate, sulfate, phosphate,alkoxide, phenoxide, alkylsulfates, arylsulfates, borates, hydrogencarbonate, carbonate, alkylcarboxylates, arylcarbonates.

The carbenes can be liberated from the corresponding salts of thecarbenes, if appropriate by reaction with an additional base. Suitablebases are, for example, metal hydrides, metal alkoxides,carbonylmetalates, metal carboxylates, metal amides or metal hydroxides.

The concentration of the catalyst, formally reported in ppm (mass) ofcatalyst metal based on the total mass, is from 0.01 ppm to 1000 ppm,preferably from 0.5 to 100 ppm, particularly preferably from 1 to 50ppm.

The ratio [mol/mol] of carbene to metal is from 0.01:1 to 250:1,preferably from 1:1 to 100:1, particularly preferably from 1:1 to 50:1.In addition to the carbene ligands, further ligands, for examplephosphorus ligands such as triphenylphosphine, may be present in thereaction mixture.

Owing to the catalyst activities and stabilities, it is possible to useextremely small amounts of catalyst in the process of the invention.Apart from a procedure in which the catalyst is reused, there is alsothe option of not recycling the catalyst. Both variants have alreadybeen described in the patent literature (WO 90/13531, U.S. Pat. No.5,254,782, U.S. Pat. No. 4,642,392).

It is often advantageous to carry out the telomerization reaction in thepresence of bases. Preference is given to using basic components havinga pK_(b) of less than 7, in particular compounds selected from the groupconsisting of amines, alkoxides, phenoxides, alkalimetal salts andalkaline earth metal salts.

Suitable basic components are, for example, amines such astrialkylamines which may be alicyclic or/and open-chain, amides, alkalimetal salts or/and alkaline earth metal salts of aliphatic or/andaromatic carboxylic acids, e.g. acetates, propionates, benzoates, orcorresponding carbonates, hydrogencarbonates, alkoxides of alkali metalsand/or alkaline earth metals, phosphates, hydrogenphosphates or/andhydroxides, preferably of lithium, sodium, potassium, calcium,magnesium, cesium, ammonium and phosphonium compounds. Preferredadditives are hydroxides of alkali metals and alkaline earth metals andmetal salts of the nucleophile of the formula (II).

In general, the basic component is used in an amount of from 0.01 mol %and 10 mol % (based on the olefin), preferably from 0.1 mol % to 5 mol %and very particularly preferably from 0.2 mol % to 1 mol %.

In the process of the invention, the ratio [mol/mol] of diene used tonucleophile used is from 1:100 to 100:1, preferably from 1:50 to 10:1,particularly preferably from 1:10 to 2:1.

The process of the invention can be carried out continuously orbatchwise and is not restricted to the use of particular types ofreactor. Examples of reactors in which the reaction can be carried outare stirred tank reactors, cascades of stirred vessels, flow tubes andloop reactors. Combinations of various reactors are also possible, forexample a stirred tank reactor connected to a downstream flow tube.

The following examples illustrate the invention without restricting thescope of the patent application.

EXAMPLES

Mes=mesityl (2,4,6-trimethylphenyl); COD=1,5-cyclooctadiene; the bondingof the heterocyclic carbene ligand to the metal is, as in the technicalliterature, shown in the form of a single bond rather than as a doublebond; TfO⁻=trifluoromethansulfonate

Example 1

Telomerization of 1,3-butadiene with methanol

211 g of degassed methanol, 589 g of 1,3-butadiene, 1.20 g of sodiumhydroxide, 50 g of cyclooctane (internal GC standard) and 0.50 g of4-t-butylcatechol were placed in a 3 liter autoclave (from Büchi) underprotective gas and heated to 80° C. 0.0494 g of palladiumacetylacetonate and 0.1078 g of the compound5-methoxy-1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazoline (from whichthe carbene B-1 can be formed by elimination of methanol) wereseparately dissolved in 48.4 g of degassed methanol under protectivegas. The reaction was started by introducing the solution (from apressure burette) into the autoclave and the course of the reaction wasmonitored by gas-chromatographic analysis of samples taken at regularintervals. After 180 minutes, 18% of the butadiene had reacted, and theselectivity of the reaction to 2,7-octadien-1-yl methyl ether was >96.8%according to gas-chromatographic analysis.

Example 2

Synthesis of the complex B-2: 60 mg of [Rh(COD)Cl]₂ (M=493.08 g/mol) aredissolved in 2 ml of THF (tetrahydrofuran) and admixed at roomtemperature with 76 mg of the carbene B-4 (M=304.3 g/mol) dissolved in 1ml of THF while stirring. The solution is stirred for 3 hours, the THFis removed under reduced pressure, the precipitate is dissolved inCH₂Cl₂ and filtered. The CH₂Cl₂ is removed under reduced pressure, theresidue is washed with pentane, filtered off and dried under reducedpressure. The yield is 82% (110 mg, M=550.97 g/mol).

Example 3

Synthesis of the complex B-3: 113.6 mg of B-2 (0.21 mmol, M=550.97g/mol), dissolved in 5 ml of THF are admixed at RT with 53 mg of AgOTf(0.01 mmol, M=256.94 g/mol) and 57 mg of PPh₃ (0.21 mmol, M=262.28g/mol) dissolved in 10 ml of THF. The AgCl which precipitates isfiltered off and the THF is removed under reduced pressure. The residueis taken up in CH₂Cl₂, filtered and part of the CH₂Cl₂ is removed underreduced pressure. The complex is precipitated from a little CH₂Cl₂ byaddition of pentane, filtered off, washed with pentane and dried underreduced pressure. The yield is 171.8 mg, 90% (M=926.88 g/mol).

Examples 4 and 5

General Method for the Telomerization of Butadiene with Methanol:

In a 100 ml Schlenk tube, the appropriate amount of catalyst isdissolved in 16.1 g of methanol under protective gas. The solution isadmixed with 1 mol % (based on the amount of 1,3-butadiene used) ofsodium methoxide (base) and 5 ml of isooctane (internal GC standard).The reaction solution is subsequently drawn into the evacuated autoclave(100 ml autoclave from Parr), the autoclave is cooled to T <−10° C. and13.6 g of 1,3-butadiene are condensed in (amount determined by loss inmass of the butadiene stock bottle). The autoclave is warmed to thereaction temperature and then cooled to room temperature after 16 hours.Unreacted 1,3-butadiene is condensed back into a cold trap cooled bymeans of dry ice. The reaction mixture in the reactor is analyzed by gaschromatography.

The telomerization of 1,3-butadiene with methanol was carried out inaccordance with the general method using the complexes B-2 and B-3. Thereaction temperature was 90° C.

The main product obtained in the reaction was 1-methoxyocta-2,7-diene (nproduct). In addition, 3-methoxyocta-1,7-diene (iso product),1,3,7-octatriene (OT), 1,7-octadiene (OD) and vinylcyclohexene (VCEN)were formed. Ex. Rh Base n + iso n:iso OT + OD + VC No. MeOH:butadieneCat. [Mol-%] [Mol-%] [%] [%] H [%] TON 4 1:2 B-2 0.021 1 4.6 97.7:2.32.4 219 5 1:2 B-3 0.021 1 1.1 95:5 2.7 52n + iso = Yield of n product and iso productn:iso = Ratio of n product to iso productOT + OD + VCH = Yield of 1,3,7-octatriene, 1,7-octadiene,vinylcyclohexene (total)TON = turnover number

1. A process for the catalytic telomerization of an acyclic olefinhaving at least two conjugated double bonds (I)

with at least one nucleophile, wherein a mixture of 1,3-butadiene withother C₃-, C₄- and/or C₅-hydrocarbons are used as said acyclic olefinhaving at least two conjugated double bonds, with alkynes and ifappropriate 1,2-butadiene being removed prior to the telomerizationreaction, and one or more complexes comprising one or more metals ofgroups 8 to 10 of the Periodic Table of the Elements and at least onecarbene ligand having one of the formulae

where R^(X1), R^(X2), R^(X3), R^(X4), R^(X5), R^(X6) are each H R²; R³:are identical or different and are each a) a linear, branched,substituted or unsubstituted cyclic or alicyclic alkyl group having from1 to 24 carbon atoms, or b) a substituted or unsubstituted, monocyclicor polycyclic aryl group having from 6 to 24 carbon atoms or c) amonocyclic or polycyclic, substituted or unsubstituted heterocyclehaving from 4 to 24 carbon atoms and at least one heteroatom from thegroup consisting of N, O, and S, R⁴, R⁵, R⁶, R⁷: are identical ordifferent and are each hydrogen, alkyl, aryl, heteroaryl, —CN, —COOH,—COO-alkyl, —COO-aryl, —OCO-alkyl, —OCO-aryl, —OCOO-alkyl, —OCOO-aryl,—CHO, —CO-alkyl, —CO-aryl, —O-alkyl, —O-aryl, —NH₂, —NH(alkyl),—N(alkyl)₂, —NH(aryl), —N(alkyl)₂, —F, —Cl, —Br, —I, —OH, —CF₃, —NO₂,—ferrocenyl, —SO₃H, —PO₃H₂, where the alkyl groups have 1-24 carbonatoms and the aryl groups have from 5 to 24 carbon atoms and theradicals R⁴ and R⁵ may also be part of a bridging aliphatic or aromaticring, wherein when the metal of groups 8 to 10 of the Periodic Table isPd, R² and/or R³ having the meaning c), are used as catalyst.
 2. Theprocess as claimed in claim 1, wherein R², R³, R⁴, R⁵, R⁶ and R⁷ areidentical or different and have at least one substituent selected fromthe group consisting of —H, —CN, —COOH, —COO-alkyl, —COO-aryl,—OCO-alkyl, —OCO-aryl, —OCOO-alkyl, —OCOO-aryl, —CHO, —CO-alkyl,—CO-aryl, -aryl, -alkyl, -alkenyl, -allyl, —O-alkyl, —O-aryl,—NH₂—NH(alkyl), —NH(aryl), —N(alkyl)₂, —F, —Cl, —Br, —I, —OH, —CF₃,—NO₂, -ferrocenyl, —SO₃H, and —PO₃H₂, wherein the alkyl groups have from1 to 24, the alkenyl groups have from 2 to 24 carbon atoms, the allylgroups have from 3 to 24 carbon atoms and the aryl groups have from 5 to24 carbon atoms.
 3. The process as claimed in claim 1, wherein anucleophile of the formula (II)R¹-Z-R^(1′)  (II) where Z is O, N(R¹″), S(O₂), Si(R¹″)(OH), C═O, C(H₂),C(H)(NO₂) or N(CH₂CH═CH₂) and R¹, R^(1′) or R^(1″) are identical ordifferent and are each H, a substituted or unsubstituted, linear,branched or cyclic alkyl or alkenyl group having from 1 to 22 carbonatoms, a carboxyl group or an aryl group, where the radicals R¹, R^(1′)may be joined to one another via covalent bonds and R¹ and R^(1′) maybear identical or different substituents.
 4. The process as claimed inclaim 1, wherein compounds of the formula (IIa) or (IIb)

where R¹, R^(1′) are identical or different and are each H, asubstituted or unsubstituted, linear, branched or cyclic alkyl oralkenyl group having from 1 to 22 carbon atoms, a carboxyl group or anaryl group and the radicals R¹, R^(1′) may be joined to one another viacovalent bonds, are used as nucleophile.
 5. The process as claimed inclaim 1, wherein water, one or more alcohols, one or more phenols, oneor more polyols, one or more carboxylic acids, one or more ammoniaand/or one or more primary or secondary amines are used as nucleophiles.6. The process as claimed in claim 1 carried out in a solvent, where thenucleophile (II) and/or inert organic solvents is/are used as solvent.7. The process as claimed in claim 1, wherein the ratio of carbeneligand to metal (mol/mol) is from 0.01:1 to 250:1.